Eris is bigger than Pluto, and it’s not going away. Many asteroids and Kuiper Belt objects can be dismissed because they are small and probably less consequential than “real” planets. But most of us have felt the power Pluto, and everything indicates we should take Eris as seriously. But what does it mean? Steven Forrest figures that it will take a generation or two for us to know the answer, but it is time to make a start.